A wireless communication system has been widely developed to provide various kinds of communication services such as voice and data. Generally, the wireless communication system is a multiple access system that can support communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of the multiple access system include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, and a single carrier frequency division multiple access (SC-FDMA) system.
In these days, it has been determined that a Multimedia Telephony Service (MMTEL) voice and video uses normal traffic channels. However, the normal traffic channels are already congested with previous providing services. Therefore, the allowing MMTEL voice and video in E-UTRAN when an Access Class Barring (ACB) is active will cause the congestion more severely.
To help reduce the congestion while at the same time providing an alternative form of human to human communication, the use of MO+MT(Mobile Terminating) SMS (which uses NAS signaling) in the congested cells should be allowed as well. Ideally the operator should be able to separately allow MMTEL voice, MO+MT SMS, or both in such situations via configuration, in order to most effectively provide some means of human to human communication whilst the congestion is being managed.